结合高能球磨和放电等离子烧结技术, 通过非晶合金粉末在烧结致密化的同时发生完全纳米晶化的机制, 制备出了致密的SmCo2纳米晶合金块体材料,其平均晶粒尺寸约22 nm. 对SmCo2纳米晶合金化合物的显微组织、晶体结构和相组成等的表征和分析表明, SmCo2纳米晶合金在室温下不能以单相的形式存在, 发生分解形成SmCo3, Sm9Co4和SmCo2多相共存的合金体系; 而粗晶合金可以SmCo2单相在室温下稳定存在.结合纳米晶热力学计算阐释了粗晶合金和纳米晶合金的相稳定性及其转变规律.对磁性能的测定表明, 与同种成分粗晶合金只有微弱的磁性能相比,SmCo2纳米晶合金表现出明显的永磁特性, 且具有良好的综合磁性能.
The nanocrystalline SmCo2 bulk alloy with an average grain size of about 22 nm was prepared by combining high–energy ball milling and spark plasma sintering (SPS), in preparation the amorphous alloy powder obtained by milling was densified and crystallized during the SPS process. The microstructure, crystal structure and phase structure of such SmCo2 were determined. These results show that the nanocrystalline SmCo2 is not able to exist stably as a single phase at room emperature and decoposes into SmCo3 and Sm9Co4 phases, different from the conventional coarse–grained SmCo2 phase, which exiss stably at room temperature. Phase stability and transformation behavior have been explained by he nanocale thermodynamic simulation. Comparing with the coarse– grained SmCo2 with very weak magnetic properties, the nnocrystalline SmCo2 exhibits remarkable permanent magnetism and good overall magnetc properties.
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